1. Field of the Invention
The present invention generally relates to photography and more particularly to an exposure aiding device for an enlarger.
2. Description of the Prior Art
Conventionally, it is known as a method for obtaining a fine contrast print to differentiate the amount of exposure for a particular region from other part of a printed image: Such conventional method is classified into "shading" method and "spot printing" method. The shading method is defined as subjecting a part of a particular region to be printed with less exposure than other part to be printed suitably. On the contrary, the spot printing is defined as subjecting a part of a particular region to be printed with more exposure, i.e. over-exposed than other part to be printed suitably.
Commonly, the ratio of exposure amount for a part which will be underprinted or overprinted to that for other part which will be printed normally, i.e. the shading amount or the exposure amount for the spot printing region and a normal exposure time have been determined according to a result of test printing, for example, of the normal exposure time and the shading amount, a normal exposure time of 10 sec. and a shading amount of 70%. The shading time is calculated by an operator such as 10 sec. .times.0.7=7 sec. However, if an aperture value of an enlarging lens or an enlarging magnification of said enlarger is changed, the normal exposure time must be changed accordingly, which causes to re-calculate the shading time. For example, if the normal exposure time is changed to 17 sec., the operator must work at a new shading time by a calculation of 17.times.0.7. Therefore, it is required for the operator to re-calculate the shading time, every time the aperture value of the enlarging lens or the enlarging magnification of the enlarger is changed, which results in a complication of the printing work. It should be noticed that such complication by re-calculation is occurred not only in the case of using the shading method, but also in the case of using the spot printing method.
Furthermore, it is often used for obtaining a fine contrast print from a negative film to select the finest print among a plurality of prints which have been printed in accordance with a plurality of the exposure amount ratios preselected. In this case, it is also necessary to re-calculate the shading time or the spot printing time respecting each of the exposure amount ratios predetermined, which results in a complication of the printing work.
The article Phototimer appearing in Electronics Today International, of September 1975, and the British patent specification No. 1,593,438 are examples of prior art timers.